I have a Beam/Regen Sentinel as well, at 50, and I love playing it. I can give some recommendations based on what I've played:
You skipped Refractor Beam and I think that's a big mistake. It's the second best AoE attack the set has behind Overcharge. I personally hate Cutting Beam so I never use it and while Piercing Beam is OK, it's just really bad for hitting more than one target because its arc is so small.
Sentinels, for better or worse, I feel require heavy damage proc usage to have decent damage output. So you can definitely squeeze out more damage with some slotting adjustments.
Related to that is taking an Epic Power Pool, most or all of them have an attack(s) that can hold a lot of damage procs and can become your highest damage dealing attack.
Here's my build, it has a good single target rotation and plenty of easily applied AoE to shred groups.